Thermally stable polyphosphonates as flame retardants

Abstract

A thermally stable flame-resistant phosphonate polymer of the structure <IMAGE> WHEREIN R1 is methyl or ethyl, R2 is hydrogen or methyl and n is 3 to 100, is formed by the reaction of acrylic or methacrylic acid with an alkyl bicyclic phosphite of the structure <IMAGE> wherein R1 is as above. The phosphonate polymer is useful in forming flame-resistant acrylic compositions such as molding powders and sheets from mixtures comprising the polymer and methyl methacrylate.

What is claimed is: 
     
       1. As an article of manufacture, an acrylic composition comprising an addition polymer formed by polymerizing a mixture comprising: a. at least 50 weight percent of methyl methacrylate; and   b. 5 to 30 weight percent of a flame-resistant phosphonate polymer defined by the general formula ##STR10## wherein R 1  is methyl or ethyl, R 2  is hydrogen or methyl and n is 3 to 100.   
     
     
       2. The acrylic composition of claim 1 wherein the mixture additionally comprising a member selected from the group consisting of isobornyl acrylate, isobornyl methacrylate and mixtures thereof. 
     
     
       3. The acrylic composition of claim 1 wherein the mixture additionally comprising an ethylenically unsaturated acrylic compound. 
     
     
       4. The acrylic composition of claim 1 wherein the mixture additionally comprising acrylic or methacrylic acid. 
     
     
       5. As an article of manufacture, an acrylic composition comprising an addition polymer formed by polymerizing a mixture comprising: a. at least 50 weight percent of methyl methacrylate; and   b. 5 to 30 weight percent of a flame-resistant phosphonate polymer defined by the general formula ##STR11## wherein R 1  is ethyl and R 2  is hydrogen and n is 3 to 100.